Spectrum DSP M2 User Manual page 53

as described below.
SSB operation with minimal speech compression:
Set the Microphone/Line gain as described in the previous section (e.g. around "0" on
•
the AUDio meter with occasional peaks to +6 to +10.)
In the menu system, set the parameter ALC Release Time to the default setting of 10.
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While speaking normally adjust the TX PRE ALC Gain parameter for a peak reading
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on the ALC meter of 4-6 dB.
Setting ALC Release Time to a higher value will reduce the compression even more.
•
SSB operation with maximum speech compression:
Set the Microphone/Line gain as described in the previous section (e.g. around "0" on
•
the AUDIO meter with occasional peaks to +6 to +10.)
In the menu system, set the parameter ALC Release Time to the default setting of 3
•
or lower.
While speaking normally, adjust the TX PRE ALC Gain parameter for a peak reading
•
on the ALC meter of 8-16 dB.
Setting ALC Release Time to a lower value and the TX PRE ALC Gain to a higher
•
value will increase the compression even more.
Explanation of the parameters and meters:
Mic Input Gain/Line Input Gain: These operate directly on the microphone and line
•
inputs in the way that you would expect. These parameters display as MIC or LIN on
the main display, respectively.
Audio meter: This displays the audio level, in deciBels, on the selected audio input,
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with "0" being the level that will just achieve 100% power at the bottom of the ALC
threshold. The level displayed is NOT filtered in any way and signals outside the
frequency range that would be transmitted (e.g. <200 Hz, >3500 Hz) will register.
TX PRE ALC Gain: This is a variable audio gain after audio filtering in the transmit
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bandpass, after the audio metering, above, but before the ALC circuit.
ALC Meter: This indicates the amount of gain reduction in deciBels that the ALC is
•
providing to the audio path. The ALC is in the audio path after transmit audio filtering
so it will not respond to audio that is outside the frequency range that will be
transmitted. The ALC can only reduce gain (by up to 40 dB) but it can never increase
it and it will settle to unity under no-signal conditions. Note that the ALC meter's
response is indicative of the ALC release time – see below.
Spectrum DSP M2 User Manual V1.1
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